Process of hardening and tempering steel.



N0. 687,7l6. Patented Dec. 3, l90l.

W. B. BENNETT.

PROCESS OF HARDENING AND TEMPERING STEEL.

(Applicafion filed Mar. 14:, 1901.)

(No Model.)

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UNITED STATES WILLIAM R. BENNETT, or

NEW BRITAIN, CONNECTICUT.

SPECIFICATION forming part of Letters Patent No. 687,716, dated December3, 1901- Application filed March 14,1901. Serial No. 51,086. (No secimens.)

To all whom it may concern:

Be it known that I, WILLIAM R. BENNETT, a citizen of the United Statesof America, residing at New Britain, in the county of Hartford and Stateof Connecticut, have invented a certain new and useful Process ofHardening and Temperin g Steel, of which the following is a description,reference being had to the accompanying drawings, wherein Figure 1 is aview, partly in section, of a hardening-tank. Fig. 2 is a view, partlyin elevation, partly broken away, and partly in central verticalsection, of an oil-tank. Fig. 3 is a view in crosssection, enlargedscale, of one of the upright pipes hereinafter mentioned.

The object of theim provement is thehardening and tempering of steel inlarge masses-- for instance, cutters, dies, and projectilesandpreventing the stock from cracking and undue shrinking, checking, andfrom having unequal internal strains.

The stock to be hardened and tempered is first heated to a desireddegree in any proper way. It is then plunged into a bath of water, whichis kept in motion where it comes in contact with the stock by freshlyinflowing streams. Any suitable fluid can be used as a cooling-bath. Atank for this work is shown in Fig. 1, wherein the letter a denotes atank, I) inlet-pipe, and c overflowpipe. From the inlet-pipe rise theupright pipes as many in number as may be desired. These upright pipesare mortised along one side, as at cl, and the incoming water findsaccess to the tank through these mortises. The heated stock is plungedinto the bath between these upright pipes cl, with the effect that theinflowing streams of water or the like keep the water and the bath inmotion where it contacts with the surface of the stock. This movement ofthe water on the surface of the stock causes the stock to be uniformlyhardened. The stock is left in the water until the vibration incident tothe cooling is about stopping, (something easily felt by an operator,who holds the stock by a pair of tongs or by a pulley-block.) It is thensuddenly drawn from the water-tank and immersed in a tank of oil,preferably animal oil. A tank for that purpose is shown in Fig. 2. Theoil containedtherein would naturally be at about the temperature of theroom-say 80 Fahrenheit. The stock is kept in the oilbath until it hasheated the oil to a desired degree, preferably until the oil and stockare practically of one temperature. There is a thermometer inside of theoil-tank for observin g temperature. After the oil has thus been heatedby the stock the gas-flames (shortly hereinafter described) are lightedabout the vessel which contains the oil, and the oil and stock areheated together up to the temperatu re required-say to 380 or 400Fahrenheit. The oil when inclosed will not flame until a temperaturefrom 550 to 565 Fahrenheit is attained. After the stock has thus beenheated to a desired temperature together with the oil the gas-flames areshut off. The stock is buried in sawdust or other proper material andallowed to cool.

In Fig. 2 the letter c denotesthe vessel which contains the oil. Theletter fdenotes a jacket outsidethe same, perforated for the inflow ofair. The letter 9 denotes a gas-pipe containing numerous apertures solocated and directed that their flames when ignited play upon the oilvessel e. By preference this coiled gas-pipe is arranged both below theoil vessel and also around it. It is of course provided with a stop-cockfor shutting off the gas when desired. The letter h denotes a cock fordrawing off the contents of the vessel e.

I claim as my improvement- 1. The process of hardening and temperingsteel which consists in, first, heating the stock, second, cooling it ina bath, third, immersing it in oil till it heats the oil to the desireddegree, and,fourth, heating the oil and stock together to a higherdegree, all substantially as described and for the purposes set forth.

2. The process of hardening and tempering steel which consists in,first, heating the stock, second, cooling itin a bath of water keepingsaid bath in motion at its contact with the stock by freshly-inflowingstreams, third, immersing the stock in oil till it heats the oil to adesired degree and, fourth, heatin g the oil and stock together to ahigher degree, all substantially as described and for the purposes setforth.

WILLIAM R. BENNETT.

Witnesses:

O. E. HART, CHAS. P. WAINRIGHT.

